eurotrans tech-talk -> BMW-transmissions -> 1991 735i (Trans Program )
Post Info TOPIC: 1991 735i (Trans Program )
bluejag69

Date:
1991 735i (Trans Program )
Permalink   

HI

I have a 1991 735i, which I love.

I have been having a problem, dash indicates TRANS PROGRAM.

This problem has been happening for several months, normally this can be cleared by stopping and then starting the car, sometimes this takes several attempts.

Normally this happens when the car is cold and after driving in limp home mode for a while, then stopping and restarting it clears its self.

I have read quite a bit of information on this problem and since it could be serious I have started with the transmission itself.

I changed the transmission filter and fluid as this is the least expensive repair. The bottom of the pan and likely the filter was pretty dirty but this had no noticeable effect and did not clear the error.

I have had my car scanned several times in the past several months the consistent trouble code which appears is Code #5.

This code points towards the Electronic Throttle control (EML)control unit. After discussions with my mechanic we replaced this part.

Before the car was going into limp home mode only intermittently, now it is constantly in this mode.

I pulled the right kick panel off to have a look at the connection and the transmission control unit (ECU some people call this the TCU)

Anyway if I was going to try and check this connection for continuity and insulation, I was horrified to see the connector. I could not even see an obvious way to open this connector.

From reading the posts of several BMW vintages it seems this message is a bit vague, and points to several different sensors possibly.

The biggest problem is that I am not a mechanic and my mechanic told me he was out of suggestions, this was worse than when I actually looked at the connector :(

Could you possible help me out.

A list of possible faults in some order would be useful

My mechanic feels sure that the transmission is ok, I would agree as the car was running great when this error gets reset.

Possible there might be a way to disable this error message permeantly with a bit of creative wiring.

I have seen some mesages regarding reflowing the solder joints on the ECU

I certainly would appreciate you help and advice.

Best Regards

Jeff

__________________
herb

Date:
Permalink   

Hi,
This 3rd version of transmission E9 is much simpler to diagnose than the older E7 version. But still it is hard to find a good workshop with the right diagnostic skills.
When I understand your explanation right, the failure seems to be on the "Throttle signal"  you have code "5" coming up. The code comes up from the control unit when it receives NO signal from the "throttle potentiometer"
it causes the computer to switch to: Mechanical emergency program
The cause of the failure is sometimes bad wire or connector problems; Or the throttle potentiometer defective.
Most of the times problems result in bad ground connectors.
Check as following
Pin 5 on TCU to 35  must have 10 volts or more    ignition on
Pin 19 on TCU to 35  must have 10 volts or more ignition on
Pin 6 on TCU to 35  must have or more 10 volts ignition on
If the ground values here are not ok, this causes the program switch to failsafe operation and a failure on pin 6 to 35 triggers a code 5
Power test as follows: When using power for troubleshooting, only use pin 35 with a fused jumper."Do not use pin 1" for testing.
use Pin 5 or 19 for negative connection
Pin 34  more as 10 volts all times
Pin 35 to minus more as 10 volts  ignition on
Pin 35 to minus engine cranking   9 volts minimum
If power or ground problems are present, this is what causes your malfunction of the transmission.
In case all is perfect then test following components.
check wires to EML (Electric throttle control)
Pin 32 and 23 on EML.
Poor connection at inter-harness connector Pin 4
I don't know at this point if your car is equipped with EML or not ? The EML system produces analog load signals similar to those found on non EML cars and they are just as easy to check. But the test procedures are different for EML version and Non EML versions.
At this point all tests so far are ok then the failure can be only the potentiometer signals. So, let us assume your car has "NO EML"
The reason of the test is, because the kickdown switch, located under the accelerator pedal, closes when the pedal is fully depressed or floored. This generates a ground signal to the TCU witch can produce a downshift depending on road speed, load and engine RPM.
The throttle potentiometer provides the primary engine load signal which is used along with the injector MS time and kickdown signal to calculate the exact engine load.
Now you understand a failure here, triggers code 5
Pin 2 on TCU with accelerator pedal travel 0-95% you must have 10 volts
Pin 2 on TCU with accelerator pedal ad kickdown point you should have 1volt
When you don't reach these values, replace the kickdown switch.
Pin 9 on TCU you must have 5 volts
Pin 9 to 6  on TCU you must have 5volts  
Pin 7 with accelerator pedal released you must have 1 volt
Pin 7 with accelerator pedal "depressed" you must have 5volts
Your values must be like I explained, if they are not ok then
it may be that Throttle potentiometer is faulty, or your wire harness is faulty between T/POT and the TCU
Let's assume you have the car with EML
The EML system provides electronic throttle control without the use of conventional cables and devices.
The transmission still requires the same throttle/load inputs as the non EML version.
A new signal called "Sport Program" is now used between the transmission and EML system. The sport signal is a high-low DC voltage. When the EML system receives this input, the throttle opening curve is increased per the standard accelerator pedal travel.The Kickdown signal is a high-low DC voltage while the throttle position signal rises and falls linearly with the throttle movement.
Pin 2 on TCU Accelerator pedal travel 0-95% you must have 5volts
Pin 2 on TCU Accelerator pedal at kickdown you must have 1volt
Pin 32 on TCU with Accelerator pedal released you must have 1 volt
Pin 32 on TCU with Accelerator pedal fully depressed you must have 10 volts
Pin 4 on TCU "sport program switch on E&M you must have 10 volts
Pin 4 on TCU  "select S program"  you must have 1volt
Should you reach non of these values your EML system is faulty or your wire harness connectors
I hope this helps you to locate your failure, in case you need more assistance let me know
herb
eurotrans


__________________
Anonymous

Date:
Permalink   

i have thye same problems but my lights goes out like i have a ect problem



__________________
Anonymous

Date:
Permalink   

SO TO IX THIS NIGHTMARE YOU DO WHAT ON A 97 540I THE TRANS FILL IS A CONSTANT ISSUE ON AGAI OFF FOR 5 MILES THEN BACK ON .REPLACE THE WIREING HARNESS ON THE TRANS OR WHAT ?REPLY TO BMW540I@Q.COM



__________________
Page 1 of 1  sorted by
eurotrans tech-talk -> BMW-transmissions -> 1991 735i (Trans Program )
Tweet this page Post to Digg Post to Del.icio.us


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard